Ortho image configuration¶
Ortho image resolution and format can be configured. Configuration options are common to all oty orthorectification sub-commands and default to sensible values when not supplied.
Resolution and alignment¶
Ortho resolution defaults to an estimate of the ground sampling distance. This can be changed with --res. The --aligned-pixels option aligns orthos so that pixel world / ortho coordinates are multiples of the resolution. When --res and --aligned-pixels are combined, orthos will be aligned on the same pixel grid. This orthorectifies the NGI aerials, aligning orthos on the same 10m pixel grid:
oty frame --dem ngi/dem.tif --int-param io/ngi_int_param.yaml --ext-param io/ngi_ext_param.geojson --res 10 --aligned-pixels ngi/*RGB.tif
Driver, data type and compression¶
Orthos can be formatted as a gtiff (GeoTIFF - the default) or cog (Cloud Optimised GeoTIFF) with --driver. The ortho data type defaults to the source image data type, and can be changed with --dtype. Compression can be configured with --compress as deflate, lzw or zstd (with any ortho data type), or jpeg (with the uint8 or uint16 ortho data types). If --compress is not specified, compression defaults to jpeg when the ortho data type is uint8, and to deflate otherwise. When jpeg compression is used with the uint16 data type, the ortho is 12 bit jpeg compressed.
Note
Support for 12 bit JPEG compression is Rasterio build / package dependent.
The next example orthorectifies using EXIF / XMP tags, and configures the ortho image as a COG with uint8 data type, and deflate compression:
oty exif --dem odm/odm_dem/dsm.tif --driver cog --dtype uint8 --compress deflate odm/images/100_0005_0140.tif
Masking and overviews¶
Valid ortho pixels are masked with either an internal mask band or a nodata value. By default, an internal mask is used when the ortho image is jpeg compressed. This avoids jpeg artefacts in invalid areas. When the ortho is deflate, lzw or zstd compressed, the default is use to a nodata value based on the data type. Masking behaviour can be changed with --write-mask to write an internal mask, or --no-write-mask to use a nodata value.
Internal overviews are added by default. This can be changed with --no-build-ovw. In this example, we create an ortho image with deflate compression, internal masks, and no internal overviews:
oty exif --dem odm/odm_dem/dsm.tif --compress deflate --write-mask --no-build-ovw odm/images/100_0005_0140.tif
Custom creation options and driver¶
For ortho image configurations not possible with the above options, custom creation options can be specified with --creation-option. The --compress option is ignored, and no other creation options are set by Orthority when --creation-option is supplied.
This example formats the ortho as a GeoTIFF with internal masks, and specifies custom creation options for 512 x 512 sized tiles, and YCbCr JPEG compression with a quality of 90:
oty exif --dem odm/odm_dem/dsm.tif --write-mask --driver gtiff --creation-option tiled=yes --creation-option blockxsize=512 --creation-option blockysize=512 --creation-option compress=jpeg --creation-option photometric=ycbcr --creation-option jpeg_quality=90 odm/images/100_0005_0140.tif